基于5-羟甲基糠醛还原胺化的多功能催化剂的构建及催化性能研究

The reductive amination of 5-hydroxymethylfurfural to 2,5-bis(aminomethyl)furan has great significance in the synthesis of biomass-based primary diamines. However, in the existing catalytic systems, tedious steps, complex and high-cost catalysts, and difficult separation have limited the development and application of the process. Our pre-experiment have also exposed several problems with the optimized catalyst Raney Ni, such as poor dehydrogenation activity for the hydroxyl group, susceptibility to the hydrogenation of furan ring, and catalyst poisoning by ammonia and organic amines. Therefore, this project intends to develop multifunctional heterogeneous catalysts for the reductive amination of 5-hydroxymethylfurfural to 2,5-bis(aminomethyl)furan, in which Ni alloying with a second metal is coated with one or more layers of nitrogen-doped graphene and is loaded on an amphoteric oxide support. So that the catalyst can be highly active and selective for the dehydrogenation, imidization and hydrogenation reactions during “one-pot” reductive amination of 5-HMF to 2,5-bis(aminomethyl)furan as well as reductive amination of other hydroxyl- or carbonyl-containing compounds. The research will focus on the formation mechanism of the multifunctional heterogeneous catalyst, the structure-activity relationship of the catalyst, the catalytic reaction mechanism, the catalytic reaction kinetics and deactivation kinetics. The implementation of the present project may offer an environmentally-benign and highly-effective synthesis approach of biomass-based chemicals, and provide new methods and thoughts for developing novel catalysts in the reductive amination of hydroxyl and carbonyl groups.

由5-羟甲基糠醛合成2,5-二氨甲基呋喃对生物基二元伯胺的制造具有重要意义。但现有催化转化体系存在步骤多、催化剂复杂、成本高、分离困难等问题。课题组前期实验中优选的雷尼镍也存在对羟基脱氢活性差、呋喃环易被加氢饱和、催化剂易受氨气和有机胺侵蚀而失活严重等缺陷。因此本项目拟选定适宜的金属与镍组成双金属，将其负载在两性载体上，然后在双金属纳米颗粒表面包覆一层或多层掺氮石墨烯碳材料制备非均相多功能催化剂，用于催化5-羟甲基糠醛“一锅法”制2,5-二氨甲基呋喃还原胺化过程中的脱氢、亚胺化和加氢反应，并将其扩展应用于其它醇和醛酮的还原胺化。深入研究掺氮石墨烯包覆的负载型双金属多功能催化剂的形成机制、催化剂构效关系、催化反应机理、催化反应动力学和失活动力学。预期研究成果将为生物质资源综合利用做出贡献，并为开发新型的羟基和羰基还原胺化催化剂提供新方法和新思路。

由5-羟甲基糠醛合成2,5-二氨甲基呋喃对生物基二元伯胺的制造具有重要意义。本项目选定适宜的金属与镍组成双金属，将其负载在两性载体上，然后在双金属纳米颗粒催化5-羟甲基糠醛“一锅法”制2,5-二氨甲基呋喃还原胺化过程中的脱氢、亚胺化和加氢反应。本项目紧紧围绕研究计划进行研究，完成了预定的研究内容，取得了预期结果。本项目研究结果包括：（1）采用VASP软件对对传统还原氨化催化剂进行结构分析和筛选，发现金属活性位点对氢气和氨气的选择性吸附能力影响其催化糠醇、糠醛、5-HMFA和5-HMF还原胺化的效率。其活性次序为：Ni>Co>Ru>Pd>Rh>Pt；（2）我们通过大量实验对第二金属和载体进行筛选，以及理论计算，发现γ-Al2O3是最优载体、NiMn双金属具有最好的活性。10Ni /γ-Al2O3和10NiMn（4：1）/γ-Al2O3分别获得了最高的BAMF产率86.3％和82.1％。尽管BAMF产率值与Raney Ni相比可以接受，但根据初始BAMF生成速率和以Ni单位质量计算10 NiMn（4：1）/γ-Al2O3、10Ni /γ-Al2O3和Raney Ni的TOF值（转化频率）分别为0.41、0.09和0.04 h-1。这对还原胺化金属催化剂的设计具有较好的借鉴意义。（3）通过这些研究，对羟基和羰基还原胺化过程中的“借氢机理”、金属催化剂筛选、催化反应条件等有了一定认识和体会，并在这些基础上提出5-HMF还原胺化催化剂需要解决的两个关键问题，即：增强催化剂对羟基的脱氢活性，和避免反应体系中氨气和有机胺对金属表面的侵蚀。（4）将这些催化理念应用于其它羟基、羰基化合物的还原胺化反应，也取得了较好的实验结果，深入研究了还原胺化催化反应的机理，为今后其他实验研究提供借鉴。